They are, says 15-year-old Federica, crouched patiently by the venue's perimeter fence, "molto profundo". For Stephania, smouldering gothically in a Cradle of Filth T-shirt, they are "even more energetic than any black metal band", while according to Anna and Erica, clear-skinned 17-year-old Led Zeppelin fans, "They make us feel something that the other bands do not." Tonight, Muse headline the 6,000-capacity Pala Vobis, a monstrous insect-shaped arena nesting in Milan's middle-of-nowhere industrial estate. Even at four o'clock in the afternoon, their appearance is hotly - not to mention very seriously - anticipated by the teenagers at the gates.

Maybe it's because of their more extreme musical tendencies, but the people who like Muse really, really like them. They're the kind of band that doesn't so much have fans as devotees. Occupying their own chill world of madness and confusion, producing music that crashes and thunders with all the dramatic passion of door-slamming, hormonal emotions - it's unsurprising that Muse should provoke an equally intense response in their audience. "Last night we had a bit of a gathering and I was chatting to people," explains singer Matt Bellamy, sitting in the band's well-appointed hotel the following afternoon, "and suddenly someone started grabbing at my neck and pulling at my chain and I was like, 'Ow, I am human.'"

He pauses pensively. "Maybe because we were semi-naked and had blue lighting wrapped around our bodies they thought we were a piece of art to be played with." Is this your usual aftershow costume? "We sometimes go to fancy dress shops and stock up on masks and lighting and novelty items," says Matt. "It makes it a bit more social when everyone's dressed up, t stops things turning into a signing session." Blue-haired drummer Dom Howard leans forward excitedly: "I've got this cool cowboy hat which is going well. White with a star on it." "I've got a massive, massive sombrero that's about four-foot wide," admits bassist Chris Wolstenholme. And Matt? "I've got a French policeman's hat with a visor that comes down so I'm behind a screen. It's like a riot helmet!" Ah, yes. Molto profundo.

When Muse first appeared with their excitable Bohemian rhapsodies for the post-grunge generation, few people envisaged that this curious musical hybrid would be capable of selling 200,000 records (as their last album, 'Origin of Symmetry' has in Britain alone) or requiring a venue the size of London's 12,500-capacity Docklands Arena. After all, they tap the mood of the times only if you happen to live in a pre-antibiotic world of syphilitic madness and over-the-counter laudanum. In 2001, where all bases are seemingly covered by nu-metal doom, gentle Buckleyesque angst and cliquey American cool, they seem like a band only a madman could love.

Yet while Muse might turn out to be modern rock's Mr Creosote - music stuffed so full of grandeur and ornament that one more wafer-thin piano phrase could make it all explode - their two albums, 'Showbiz' and 'Origin of Symmetry', have struck a suitably epic chord with an increasingly large audience. "Often we'll verge on embarrassing territory, a certain over-the-topness," laughs Matt. "But maybe that's just trying to unveil something that's inside all of us. If you extracted the bass drum and the guitar and the microphone and put me in a lonesome room at certain moments in the set I'd look like an embarrassing screaming maniac. A little bit laughable, maybe." Hysteria, however, is breaking out at Pala Vobis even before 'Plug in Baby' gets a chance to whip itself into a frenzy. Today's major topic of conversation are the news reports claiming two 14-year-old boys in southern Italy stabbed a girl "in honour" of Marilyn Manson. Last year, Manson was held responsible for the behaviour of three schoolgirls who were found guilty of murdering a nun as she walked through their sleepy small town. Rock'n'roll is not getting a particularly good press in Italy at the moment.

"Is that alienation?" sighs fan Stephania wisely. "It depends what goes on in your head. It's not Marilyn Manson who makes you kill people. It's not Matt Bellamy who makes you alienated. There are kids who listen to classical music who are alienated." You think of Bellamy, a fan of Berloiz, pounding away at the piano with increasingly baroque abandon, a Phantom Of The Opera who can set his sights beyond Sarah Brightman, and you think, maybe she has a point. The band say they've noticed a preponderance of Slipknot T-shirts in their audience, yet Muse's take on the evergreen alienation schtick has little to do with all-out, counsellor-worrying rage.

Just as the Manics had their wave of self-mutilation, The Smiths encouraged celibacy and floral tributes, and Suede empowered the sexually ambivalent, Muse offer something for those who realise that pondering death's sting to a bedroom soundtrack of Rachmaninov is more likely to startle your parents and impress your peers than Identikit fits of nu-metal petulance. "I don't know anyone who is an insider," Matt will say. "I don't know anyone who's completely...'borg'." Maybe it's no coincidence that the tour soundtrack is shaping up to be The Smiths. Matt quotes lyrics from 'Half A Person' and 'How Soon Is Now?' in conversation, while 'The Best Of The Smiths' forms an incongruous soundtrack to their aftershow gathering in the bunker-like Pala Vobis dressing room. As 'Please Please Please Let Me Get What I Want' plays plaintively in the background, a clutch of beautiful Milanese girls pick their way through the trails of blue fairy lights. One, you notice, is already wearing the riot helmet.

It's not just Italian goths who have taken Muse to their theatrical hearts, however. Despite initial derision from their homeland, Muse's domestic position is strengthening at an impressive rate. As the hotel's cabaret piano ripples genteelly in the background, Muse address the implications of their surging fame and the size of the Docklands show. "I think it's a bit too big, maybe," admits Matt, who talks like he plays the piano, the drumming of his fingers later threatening to drown out the tape. "But Dom thinks it's alright. Dom wants to be a stadium rock drummer and have a sweat towel tech. We're working a lot with videos so you get close-ups of pianos and Dom's bass drum - things you wouldn't even see in a pub gig. Extreme close-up and extreme distance at the same time, which I think goes with the music."

He's right. For while their songs might deal with space and scars and "puppet strings to our souls", Muse would rather hang out with their fans than encourage them to write letters in their own blood, revelling in the sense of community they experience while on the road. Matt gets almost emotional about the video shoot for new single 'Hyper Music'/'Feeling Good' where fans were bussed in as extras. "I could see people looking at us a bit funny," explains Matt. "So I just went in when this guy was telling them all to stand behind a line and stay there I went round the back and got in there with them. "It got to me," he twitches. "I saw something, I saw something...I saw some beauty for a moment...A weird amount of friendliness. That really got to me - I got a feeling of what it was like for other people to be into the music." And they all laugh.

Bands usually prefer to depict themselves as the moody outsiders, misunderstood, like an unholy mix of Marlon Brando and James Dean - even if they were actually prefects who captained the football team and got Valentines from half their year. After all, only Limp Bizkit fans crave a band who is an establishment. In theory, Muse - mocked by their peers, considered 'weird', at odds with the prevailing consensus - should understand genuine teenage outsiderdom. "I was friends with everyone," says Matt, contradictorily. "I used to do a lot of drama in school - we used to go away on trips to nice places that were haunted and do improvised activities. Dom used to take the piss out of me but the truth is I was doing it because there was this girl I wanted to have sex with." "It was the start of our first band," explains Dom wryly. "We'd go and do a band practice and I'd look round for Matt and find him in tears in a drama group somewhere. 'Get a grip - let's go and rock.'"

"All the people who were really popular at school are mechanics now," says Chris quietly. "I used to hang round with the well-hards," admits Matt, wrecking any image of sensitive alienation. "We used to go down town and get fucking pissed up and get in fights...and I'd watch. I was a good defender in football. The first year of school I made everyone laugh but my comedic abilities disappeared by the third year. Then I started hanging around girls. It was Dom who belonged to the group of "guys with long hair who liked guitar music". Matt makes a confession: "When I first joined your band I was wearing Umbro tracksuits." Dom: "Shell suits and a flat-top..." Yet just as you start thinking Muse are no strangers to popularity, odd figureheads for the disenfranchised, Matt lets his smile slip.

"We made the choice not to go to University and it did get a bit dark for a couple of years," he explains. "It made us go into a three a little more, make music that was pleasing to each other. To the point we could play to one person who didn't give a shit and still have a really good time. It made us not care what anyone else thought. But maybe the way we deal with that is making music that's saying, 'Fuckkk offf'." He says this with such Linda Blair-like intensity, a low and furious snarl, that it's actually quite alarming. After all, they're only 23 - and the scars of their hometown troubles still run deep. You only have to look at all the scally/mosher nonsense in Manchester to see this is an ongoing, generational thing - basically, having weird hair still causes trouble.

"When we go back to Teignmouth everyone hates us because they think we slag it off. They say it's beautiful; lovely beaches, people leave their doors open...but for 15-year-old kids it's just drugs and fights. "The cash machine was opposite the arcade," Matt explains, "and all the hard nuts would hang around by the gambling machines. Every time we went to get some money out, it was a war zone. You'd think no-one had seen us and then someone would go '(Grunts) You just call me waaaanker?' and you'd go 'What?'. And then two guys would run over and beat Dom up. It was horrendous."

"These weren't people from school," explains Chris. "These were older men who hang out with 14-year-old girls." "They drive yellow Capris with dice in the front and deal drugs to children, basically," continues Matt. "There's only ever about four or five of them at any one time because they always end up in prison or dead." He looks pensive: "I do secretly get the urge to go back and..." Chris: "Pull out a couple of grand?" Matt pauses for a second: "Pull out a gun."

Sitting on a tourbus with suitably deviant lilac leather seats, Matt's talking about violence again. He's thrumming with energy, replacing yesterday's air piano with twanging the elasticated bracelets round his wrists. "I've had some severe incidents of road rage recently," he says. "It's always these old guys, 60 or something. I'm sure I've done nothing wrong. There's this one time I parked up on the kerb illegally so I could use a cash machine and this car deliberately rubbed up against my car to prove a point. I was like, 'FUCK OFF'." He says this with the same alarmingly intense snarl as we heard yesterday. "And because he saw me say that, this old guy got out with a crowbar and started cracking the lights. It was my mum's car as well. I just sat in the car laughing at him because I couldn't believe how tragic it was. I had a video camera with me and I was filming him do it and he started shaking with embarrassment knowing everything he'd done had been captured. I've still got that video somewhere. A policeman wouldn't do that, would they? But policemen, teachers, bouncers, fucking security guards... I feel that they don't trust or like me automatically, and I haven't even done anything. I just walk into a room and I feel like a target.

"I used to get thrown out of clubs all the time," he remembers. "Once somebody picked me up by the neck and literally threw me out of the door." What were you doing? "I was dancing a bit weirdly and I think it looked like I was taking the piss." Do you go out of your way to provoke people? "Not really, because it means I get beaten up and I'm not very big. Although, I've never been badly beaten up - just thrown around a bit." Do you think that your feud with Stereophonics followed a similar pattern? They were the bouncers, you were the ones dancing weirdly...

"It did have a smell of the same thing. Maybe they know - not them necessarily, but people like that, who hate what I do - that I could not give a shit and that I am having the best time of my life. It happened again the other day. I was walking into the Astoria and some guy tried to start a fight with me, calling me a 'fucking wanker, pompous twat', the usual sort of stuff. The only time I would let it get to me is if he hit me. Otherwise I just laugh." It's a fairly well-trodden lexicon of madness Muse tread - the histrionics of 'Micro Cuts' or 'Screenager', the sense of a chill future, the references to blood and loneliness. What do you think you bring to those conventions? "I'm not completely self-absorbed," he smiles. "What I know of this world is what my senses have told me so in a way exploring the world is exploring your own self. In the process of going there you hit a certain Jacob's Ladder-type madness where you face your own worse fears and dreams. I think it's on the edge of madness. I can feel it sometimes when I'm on stage, moments of insanity, a complete sort of 'I don't know what's happening', an utter lostness. Like ventriloquism or Being John Malkovich."

For all the trappings of rock stardom and sophistication that surround Muse on the road - Matt's specially-made Japanese-style silk top, the attractive young women, the nightclubs that stay open just for them - it's not hard to see an underlying nerdiness poking through the self-confidence, Matt's intensity occasionally tripping him up. "I don't want to say the next stuff, it just sounds so laughable," giggles Matt. "If you print this people will think I'm a mental person. I try to express a lot about how I feel about the evolution of us. Hopes and fears about the future. The possible direction we're all going in.

"The name of the album, 'Origin Of Symmetry', is from a book about geometry of the universe and how it's all in beautiful balance, a perfect thing in ten dimensions. It explains all the mysterious forces we invented religions around." He unleashes an analogy of how mankind is like a worm crawling across a piece of paper. He talks of mysterious catacombs in southern Iraq and mysterious tablets predating language. He has the good grace to laugh a lot. "When I was out in Boston, the Pentagon got bombed," he explains. "There was a person out there who had a friend who used to be a pilot and he was worried his friend was dead. In the heat of the moment he started talking about all this stuff and nodded us in the direction of a few websites and books.

"It all sounds a bit unbelievable but there's definitely something there. They found these tablets that are in a computer language, full of star charts. There's an 11th planet which is actually geothermal and there's life on it and when it comes within reach of our planet they come over. They deliberately cloned us to one fifth of their intelligence and we only use a fifth of our brain." He shrugs and laughs: "I entertain that sort of possibility a lot. I don't necessarily believe any of them. But it's important people should know. You go into a physics lesson at school and they get out a Bunsen burner."

Like a ludicrous and labyrinthine conspiracy theory, a Muse show is an impressively convoluted, massively entertaining event. As Chris tries to bayonet the front rows with his bass and Dom lets the drumkit remove all his inhibitions, Matt channels an unearthly falsetto and leaps upon his piano and throws red 'petals' from the sleeves of his geisha blouse. At the end of the show, after the lights come up, Dom and Chris sweetly run onstage and spray the audience with champagne. Are Muse the band to give a voice to those who are too sensitive to contemplate nun-killings but to tough to accept the status quo? Or just three young men with a vast talent for the grand gesture having the time of their lives? Matt should probably have the last word. "I think beliefs are just when you conclude on the knowledge you've obtained so far and the trouble is once you've made that conclusion you block yourself to new things," he said earlier. "So I think it's generally good never to conclude."

This week's revelations about aliens are the latest in a long line of great Muse-ings... "I saw a programme once about Psywar and the influences that governments have over their populations in order to make them believe they're having a war for the right reasons, things like that. How they can use mobile phones; they use the microwaves inside to do stuff to us."

"I want to get lots of balloons filled with confetti and buy along-range pea shooter and shoot them as they fall over the audience whilst philosophising over the purpose of the little finger and index finger rock hand gesture. I plan to enjoy myself, to look at you and kiss you on the ridge of your nose, and your two twin friends." - Matt's 'plans for the festival season'. "To an elephant it would probably seem inaudible and to a mouse my highest note would be a rumble. It's relative." - Matt on 'that voice'.

"(Madonna) will probably be on her knees giving me a blowjob with three of her mates one day but I'll have to sell ten million records first and have a body like Ricky Martin."

"It's about a semi-fear of the evolution of technology and how in reality it's destroying all humanity. My fear is that we can't control it because it's moving faster than we are, so the song's setting myself in a location where the body is no longer important and everyone's plugged into a network." - Matt on 'Plug In Baby'

"To find out where the origin of symmetry is would be to find out if God exists." "I was having these strange hallucinations of this triangular blade, really silver metallic, razor sharp. I was in this landscape, arid, grey, dead with an endless horizon and I was trying to dodge these blades that were flying about everywhere. They'd go into my head and I could feel them cutting into my brain... The I went to the doctor and he told me to drink more water and that was that."

"We went to some temples in Osaka and there were lots of girls and young women with their faces painted white, praying and chanting. It was just about the hottest thing I've ever seen."

"We finished the first five songs of the album and then we woke up one morning and there was a field of mushrooms right next to the studio. So we ate them all. We had to have everything remixed because we were all in a Jacuzzi together eating maggots."